A forging press is known having a press frame which carries a pressing table adapted to receive the workpiece and which has a generally horizontal driveshaft carrying an eccentric driver that is in force-transmitting engagement with a vertically reciprocal hammer. The stroke of the hammer is established by the eccentricity of the eccentric driver.
It is known to adjust the lower limit of the piston stroke by means of a relatively complicated arrangement that displaces the rotation axis of the shaft carrying the eccentric driver. Thus the driveshaft is itself journaled eccentrically in a pair of sleeves or bushings which can be rotated by means of gearing.
This system has been combined with an overload protector whereby when the upward force exerted on the driveshaft by the hammer exceeds a predetermined force on eccentric bushing mounting this driveshaft may rotate, thereby preventing the press from damaging itself or the workpiece through overload. This system has the considerable difficulty that such an overload protector puts the apparatus out of adjustment. In addition it is very difficult to arrange the system such that the overload protector will only be effective at a predetermined force, as the angular positions of the adjustment-bushing axis and driveshaft axis determines the amount of upward force transferred as angular force to the eccentric bushings.
Another known system allows adjustment of the forging press by raising and lowering the working table. This is effected by means of wedges displaceable under the table. Such an arrangement is disadvantageous in that the position of these wedges underneath the work table exposes them to the injurious effects of workpiece chips and oil that tend to drain off the table.